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Digitale Medien

The true unit cell of ammonium hydrogen sulfate, (NH4)3H(SO4)2 (1984)

Davis, B. L. ; Johnson, L. R.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 17 (1984), S. 331-333

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: A combination of X-ray powder diffraction and single-crystal Laue photography was used to determine the unit-cell parameters for letovicite. μr = 247.25. The unit cell is triclinic, P1 or P{\bar 1}, and has dimensions a0 = 5.87(1), b0 = 10.17(3), c0 = 8.27(1) Å, α = 101.1(4), β = 111.1(1), γ = 89.9(2)°, V = 450.7 Å3, Z = 2, Dx = 1.82 Mg m−3. The M(20) cell reliability is 23.8. Many weak powder spectra were observed, which preclude the possibility of monoclinic cell symmetry previously reported. Projection of the letovicite Laue data along [001] reveals the striking pseudo-hexagonal symmetry observed optically. The JCPDS Diffraction File No. for ammonium hydrogen sulfate is 35-1500.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889884011596

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Digitale Medien

Examination of the solid phases in the system AgI–NaI–H2O (1972)

Johnson, L. R. ; Davis, B. L.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 5 (1972), S. 194-200

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: By means of several low temperature devices the solid hydrous phases of the AgI–NaI–H2O system have been extensively studied by X-ray diffraction, transmission Laue photography, and polarizing microscopy. The density, composition and unit-cell parameters have been determined for three distinct AgI–NaI hydrates for which the stability regions correspond to phases C, E, and F previously reported by Davis [J. Atmos. Sci. (1969), 26, 1042]. The cell assignments are based on determinations of axial ratios from the Laue photographs and interplanar spacing analyses utilizing the Hesse–Lipson technique, Cohen cell-parameter refinement and the de Wolff cell-reliability criteria. All phases are of the composition AgI–NaI–nH2O with phase C at 25 °C having n = 4, ρ = 3.0 g.cm−3 (measured and calculated) and indexing on the basis of a monoclinic cell with parameters a0 = 7.573, b0 = 9.454, c0 = 12.403 Å, and β = 92.43° with Z = 4. Phase F at −10 °C is also monoclinic with a0 = 5.757, b0 = 13.563 and c0 = 12.541 Å and β = 103.05° with Z = 4, and n = 4. Phase E appears to consist of two structures, very similar but differing in cell volume by 2.8%. We believe this to be due to varying water content, the n = 3 phase being metastable. The cell reliability factor is less than 10 for both cells and indexing is considered to be tentative.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889872009197

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Digitale Medien

The phases of the AgI–KI–H2O system (1975)

Johnson, L. R.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 8 (1975), S. 507-514

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: An X-ray diffraction study of the AgI–KI–H2O chemical system was conducted by injecting an acetonic solution of a 2:1 mole ratio of AgI:KI directly upon an inert substrate thermally strapped to a thermoelectric cold stage. The atmosphere over the stage was controlled from 0.6 mb water vapor pressure to saturation while the temperature was varied from −22 to 25°C. Under these conditions four distinct crystalline phases are formed. Crystals of phase AK (KAg4I5) appear as the acetone evaporates. Moisture available from the ambient atmosphere functions as a catalyst as the newly formed AK transforms to phase BK (K2AgI3). At higher vapor pressures a second transformation results in phase CK. All phases break down and form an aqueous solution of KI plus equant AgI crystals (complex DK) at saturation vapor pressures. Another hydrous phase EK occurs below 0°C. The most probable composition of phases CK and EK is KAg2I3.H2O and KAg3I4.8H2O respectively. Nucleation studies show that the KI system is a poorer artificial nucleant of ice than the NH4I–AgI system above −10°C. Kinetics of the system suggest an absence of any free AgI for aerosols released from airborne platforms or from ground seeding stations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889875011144

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Digitale Medien

The true unit cell of ammonium hydrogen sulfate, (NH4)3H(SO4)2. Errata (1986)

Davis, B. L. ; Johnson, L. R.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 19 (1986), S. 274-274

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: Recently discovered errors in sample preparation for the original study by Davis & Johnson [J. Appl. Cryst. (1984). 17, 331–333] have revealed that the reference intensity ratio data of Table 1 are incorrect. The reference intensity ratios for the three sets of reflections given in Table 1 have been remeasured and are as follows: 020 + 1{\bar 1}0 = 1.92; 021 + 002 = 1.16; and 1{\bar 3}0 = 0.88. The resulting average reference intensity ratio for the letovicite 111 reflection (the strongest of the pattern) is 1.15(5). Fortunately, the reference constant study was completed independently of the powder diffraction and Laue study and hence the cell constants, diffraction intensities and spacings presented in this paper are not affected by these errors.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889886089434

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Digitale Medien

Stabilities and cell parameters for phases of the AgI–NH4I–H2O system (1976)

Johnson, L. R. ; Davis, B. L.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 9 (1976), S. 98-105

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: The density, composition, X-ray powder data, unit-cell parameters, and stability fields are reported for five phases of the AgI–NH4I–H2O chemical system. The determinations were made by X-ray powder diffraction but with some aid from polarizing optical microscopy. Provisional cell assignments are: phase An (4AgI.NH4I) is cubic, phase Bn (3AgI.NH4I.6H2O) monoclinic, phase Cn (AgI.2NH4I) orthorhombic, phase E〈inf/〉n (AgI.2NH4I.H2O) orthorhombic, and phase Fn (2AgI.NH4I.2H2O) monoclinic. Upon combustion of an acetone solution of silver iodide and ammonium iodide, phase An forms and, when injected into the atmosphere, transforms to phases Fn or Bn as determined by the available moisture and temperature.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889876010698

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Compositional variations in glauconite (1984)

Buckley, H. A. ; Easton, A. J. ; Johnson, L. R.

Mineralogical Society of Great Britain and Ireland

In: Mineralogical Magazine. 1984; 48(346): 119-126. Published 1984 Mar 01. doi: 10.1180/minmag.1984.048.346.16.

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Publikationsdatum: 1984-03-01

Beschreibung: Variation in composition, Fe3+/Fe2+ ratio, per cent mixed-layering, and d(060) spacing have been determined both between and within grains of glauconite from the Folkestone Beds at 286.5 m in the Tollgate bore, Sandwich, Kent. Grains extracted from the rock were classified on the basis of size into large (〉 1 mm) and small (〈 1 mm), and on colour into light and dark green. Large grains have a progressive increase in Fe3+/Fe2+ ratio with increase in total iron, while small grains have variable ratios; the largest variation is in the dark grains. The effect of the range of Fe3+/Fe2+ ratio variations on structural formula (e.g. R3+) is discussed. The per cent mixed-layering is not related to colour. There is a greater variation in Al, Fe, and K contents in and between large grains than small grains. Both sizes of grains may be separated on d(060) spacings determined by X-ray diffraction. Glauconite from coral and gastropod casts has different d(060) spacings than that from bryozoan casts and variegated grains, but is similar to the small grains. Large light grains may have developed from small light grains but it is unlikely that the large dark grains developed from small dark grains. The large grains probably all formed under similar conditions, with a common origin; the small from several sources or from a single source under a variety of conditions.

Print ISSN: 0026-461X

Digitale ISSN: 1471-8022

Thema: Geologie und Paläontologie

Publiziert von Mineralogical Society of Great Britain and Ireland

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Glauconite and celadonite: two separate mineral species (1978)

Buckley, H. A. ; Bevan, J. C. ; Brown, K. M. ; [weitere]

Mineralogical Society of Great Britain and Ireland

In: Mineralogical Magazine. 1978; 42(323): 373-382. Published 1978 Sep 01. doi: 10.1180/minmag.1978.042.323.08.

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Publikationsdatum: 1978-09-01

Beschreibung: SummaryAnalyses of glauconites and celadonites from continental sedimentary rocks and sea-floor basalts using X-ray diffraction, electron probe microanalysis, infra-red spectroscopy, and X-ray fluorescence spectroscopy are reported. The minerals are shown to be distinct species; each an isomorphous replacement series, glauconite having an average half unit cell of K0·85(Fe3+, Al3+)1·34 (Mg2+, Fe2+)0·66(Si3·76Al0·24)O10(OH)2 whereas celadonite approaches the ideal half unit cell of K(Fe3+, Al3+)(Mg2+, Fe2+)Si4O10(OH)2. Considerable Fe3+Alvi interchangeability occurs in the octahedral layer in both minerals and considerable substitution of aluminium in the tetrahedral layer of glauconites results in the more disordered 1Md type of structure compared with the more highly ordered 1M structure of celadonites. Some mixed layer glauconite-smectites and celadonites were also examined and could be distinguished from true glauconites and celadonites by chemical analysis, XRD, and IR techniques. It is proposed that the terms ‘glauconite’ and ‘celadonite’ should be used only for those minerals containing less than 5% interlayering.

Print ISSN: 0026-461X

Digitale ISSN: 1471-8022

Thema: Geologie und Paläontologie